Rebar (typically elongated steel bars or rods) is placed in concrete structures to add tensile and shear strength (i.e., resistance to forces stretching the concrete structure apart) to its inherent compressive strength (i.e., resistance to forces pressing on it). The steel has to be placed in the proper location in the concrete structure to provide maximum resistance to compressive, tensile and shear pressures and help control cracking. In a concrete wall, horizontal reinforcement adds resistance to tensile forces, and vertical reinforcement improves resistance to shear forces. The vertical and horizontal rebars are connected to form a web or grid pattern inside a concrete form prior to pouring the concrete. It is important that the rebar maintains its location and proper spacing between the bars to ensure that the rebar is completely covered after the concrete sets.
One of the most commonly used methods to construct a rebar reinforced concrete wall is to use tie wire to secure the horizontal bar to the vertical bar. In addition, rebar beam bolsters can be used to properly space the horizontal bars from the walls of the concrete form work. After the vertical rebar are installed, the ironworker typically holds the horizontal rebar in position while wrapping a tie wire around the vertical bar to connect the two pieces together. The horizontal rebar are installed sequentially starting at the bottom and the ironworkers climb up the rebar grid as they construct it.
The reinforcement of concrete walls with an internal steel frame fabricated from rebar is well known. FIGS. 1-4 show prior art constructions that connected vertical and horizontal rebars with wire ties. FIG. 1 shows the attachment of set-up bars (i.e., the vertical rebars) to a form wall and the marking of the location of the horizontal rebars with white dots (FIG. 2). The horizontal rebars are placed at the designated elevations and attached to the vertical rebars with a wire tie as shown in FIG. 3. The attachment of a plurality of horizontal rebars to the plurality of set-up bars forms a grid structure (FIG. 4). The concrete is poured into the form and the rebar grid strengthens the concrete structure after the concrete sets.
The methods and rebar used to form rebar reinforcement structures are time and labor intensive as well as an immense waste of resources and materials. It would be desirable to have a system that eliminates the need for cutting slab bolsters into pieces and having to tie vertical set up rebar and manually mark out spacing. There is also a need for a method for constructing rebar grids that eliminates the need for the ironworker to manually hold the horizontal rebar in position while it is secured to the vertical rebar.